PoE power monitoring arrangement and method

ABSTRACT

A method for monitoring power delivered to a powered device over communication cabling, the method comprising: enabling a first supply power; enabling a second supply power; for the enabled first supply power, providing a first maintain power signature (MPS) functionality arranged to disable the enabled first supply power in the event that the current drawn from the enabled first supply power is less than the first undercurrent threshold; for the enabled second supply power, providing a second maintain power signature (MPS) functionality arranged to disable the enabled second supply power in the event that the current drawn from the enabled second supply power is less than the second undercurrent threshold; receiving an indication that the powered device presents a single powered device interface to both the first and the second PSE; and controlling one of the provided first and second MPS functionality responsive to the received indication.

BACKGROUND OF THE INVENTION

The invention relates generally to the field of power over local areanetworks, particularly Ethernet based networks, and more particularly toa method of monitoring power drawn by a powered device receiving powerover four twisted wire pairs.

Power over Ethernet (PoE), in accordance with both IEEE 802.3af-2003 andIEEE 802.3at-2009, each published by the Institute of Electrical andElectronics Engineers, Inc., New York, the entire contents of each ofwhich is incorporated herein by reference, defines delivery of powerover a set of 2 twisted wire pairs without disturbing datacommunication. The aforementioned standards particularly provide for apower sourcing equipment (PSE) and a powered device (PD). The powersourcing equipment is configured to detect the PD by ascertaining avalid signature resistance, and to supply power over the 2 twisted wirepairs only after a valid signature resistance is actually detected.

U.S. Pat. No. 7,492,059 issued Feb. 17, 2009 to Peker et al, the entirecontents of which is incorporated herein by reference is addressed topowering a PD over 4 twisted wire pairs. Such a technique provides forincreased power as compared to either of the above mentioned standards,and is commercially available from Microsemi Corporation of Alisa Viejo,Calif.

The HD BaseT Alliance of Beaverton Oreg. has published the HDBaseTSpecification Version 1.1.0 which defines a high power standardutilizing twisted wire pair cabling, such as Category 5e (CAT 5e) orCategory 6 (CAT 6) structured cabling as defined by ANSI/TIA/EIA-568-A.The specification provides for even higher power than the abovementioned IEEE 802.3at-2009 over each set of 2 pairs, with all 4 pairsutilized for powering, and allows for power over structuredcommunication cabling from any of: a type 1 PSE, denoted hereinafter asa low power PSE, typically meeting the above mentioned IEEE 802.3afstandard; a type 2 PSE denoted hereinafter as a medium power PSE,typically meeting the above mentioned IEEE 802.3at standard; a type 3PSE, denoted hereinafter as a high power PSE, typically meeting theabove specification; twin medium power PSEs; and twin high power PSEs.

Detection, in accordance with any of the above standards requires thesupply of at least 2 voltage levels between the range of 2.8 volts and10 volts, with a signature resistance of the PD determined based on acalculation of the actual voltage levels, or current, detected. The useof 2 voltage levels allows for determination of the signature resistanceirrespective of the existence of a diode bridge, typically supplied atthe input to the PD. The voltage levels may be impressed via either acurrent source, or a voltage source.

FIG. 1A illustrates a high level block diagram of a PoE poweringarrangement 10, according to the prior art, comprising: a switch/hub 20;a plurality of twisted wire pairs 30 constituted within a structuredcable 35; and a PD 40. Switch/hub 20 comprises a plurality of datatransformers 50 and a first and a second PSE 60 and a master control 63.PD 40 comprises: a plurality of data transformers 50; a first and asecond diode bridge 65; a PD interface 70; an electronically controlledswitch 80; and a PD load circuitry 90. PD interface 70 comprises: anunder-voltage lockout (UVLO) circuit 100; a signature impedance 110; anda class current source 120. Optionally, a class event counter is furthersupplied (not shown). As illustrated in FIG. 1B, PSE 60 comprises: acontrol circuitry 61; a sense resistive element, illustrated anddescribed herein without limitation as a sense resistor RS; and acurrent limiter CL, illustrated and described herein without limitationas an n-channel metal-oxide-semiconductor field-effect-transistor(NMOSFET). Control circuitry 61 comprises: a detection functionality 62;a classification functionality 64; a powering functionality 66; and amaintain power signature (MPS) detection functionality 68, each of whichmay be constituted in a dedicated circuitry, or as a programmedfunctionality for a computing element, without limitation. Each controlcircuitry 61 is responsive to master control 63 (connection not shown).In one embodiment, a selected control circuitry 61 further acts asmaster control 63 and communicates commands to other associated controlcircuitries 61.

A data pair is connected across the primary winding of each datatransformer 50 in switch/hub 20 and a first end of each twisted wirepair 30 is connected across the secondary winding of each datatransformer 50 in switch/hub 20 via respective connections, listedconventionally in two groups: connections 1, 2, 3, 6, denoted ALT-A,where power is thus delivered over a first set of wires; and connections4, 5, 7 and 8, denoted ALT-B, where power is thus delivered over asecond set of wires. A first output of first PSE 60, representing thepositive polarity, is coupled to the center taps of the secondarywindings of data transformers 50 of switch/hub 20 connected to twistedwire pairs 30 via connections 1 and 2; and a return of first PSE 60,which as shown in FIG. 1B is associated with the drain of NMOSFET CL, iscoupled to the center taps of the secondary windings of datatransformers 50 of switch/hub 20 connected to twisted wire pairs 30 viaconnections 3 and 6. A first output of second PSE 60, representing thepositive polarity, is coupled to the center taps of the secondarywindings of data transformers 50 of switch/hub 20 connected to twistedwire pairs 30 via connections 4 and 5; and a return of second PSE 60,which as shown in FIG. 1B is associated with the drain of NMOSFET CL, iscoupled to the center taps of the secondary windings of datatransformers 50 of switch/hub 20 connected to twisted wire pairs 30 viaconnections 7 and 8. The powering arrangement associated with first PSE60 is conventionally known as ALT-A powering, i.e. wherein powering isprovided over the set of wire pairs associated with connections 1, 2, 3and 6; and powering from second PSE 60 is conventionally known as ALT-Bpowering, i.e. wherein powering is provided over the set of wire pairsassociated with connections 4, 5, 7 and 8.

The gate of NMOSFET CL is coupled to an output of control circuitry 61.The source of NMOSFET CL is coupled to a first end of sense resistor RSand a respective input of control circuitry 61. A second end of senseresistor RS is coupled to a respective input of control circuitry 61 andto a return line 130 coupled to a return of a power source (not shown).A power line 140, coupled to the power output of the power source (notshown) represents the positive polarity output of PSE 60. Structuredcable 35 typically comprises 4 twisted wire pairs 30.

A data pair is connected across the primary winding of each datatransformer 50 in PD 40 and a second end of each twisted wire pair 30 isconnected across the secondary winding of each data transformer 50 in PD40 via respective connections, listed conventionally in two groups:connections 1, 2, 3, 6; and connections 4, 5, 7 and 8. The inputs offirst diode bridge 65 are respectively connected to the center taps ofthe secondary windings of data transformers 50 of PD 40 connected totwisted wire pairs 30 via connections 1, 2, 3 and 6. The inputs ofsecond diode bridge 65 are respectively connected to the center taps ofthe secondary windings of data transformers 50 of PD 40 connected totwisted wire pairs 30 via connections 4, 5, 7 and 8. The positiveoutputs of first and second diode bridges 65 are commonly connected tothe positive input of PD interface 70, and the returns of first andsecond diode bridges 65 are commonly connected to the return of PDinterface 70. PD interface 70 is illustrated as having a pass throughconnection from the positive input to the positive output thereof, andpower for each of UVLO circuit 100, signature impedance 110 and classcurrent source 120 are provided there from (not shown). PD interface 70is illustrated as having a pass through connection from the return inputto the return output thereof, and a return for each of UVLO circuit 100,signature impedance 110 and class current source 120 are provided therefrom (not shown). Electronically controlled switch 80 is arranged toprovide a switchable connection between the return of PD load circuitry90 and the return of PD interface 70, and electronically controlledswitch 80 is responsive to an output of UVLO circuit 100, indicativethat received power is reliable and is denoted PG. The positive input ofPD load circuitry 90 is connected to the positive output of PD interface70.

Powering arrangement 10 has been illustrated in an embodiment whereinelectronically controlled switch 80 is connected in the return path,however this is not meant to be limiting in any way and in anotherembodiment electronically controlled switch 80 is connected in the powerpath. Similarly, PSE 60 is illustrated as being part of switch/hub 20however this is not meant to be limiting in any way, and midspanequipment may be utilized to provide a connection for PSE 60 withoutexceeding the scope. PSE 60 may be any equipment arranged to providepower over communication cabling, including equipment meeting thedefinition of a PSE under any of IEEE 802.3af; IEEE 802.3at; and theabove mentioned HDBaseT specification, without limitation.

In operation, electronically controlled switch 80 is initially set toisolate PD load circuitry 90 from PSE 60. Each of first PSE 60 andsecond PSE 60 acts to detect PD 40 utilizing detection functionality 62in cooperation with signature impedance 110 presented by PD interface70. After detection, PSE 60 optionally presents a classification voltageto PD 40 utilizing classification functionality 64, and class currentsource 120 is arranged to drive a predetermined current indicative ofthe power requirements of PD load circuitry 90 responsive to thepresented classification voltage, thus indicating to PSE 60 the powerrequirements thereof. The amount of current is detected byclassification functionality 64. Optionally, PSE 60 further provides PD40 with information regarding the powering ability of PSE 60 byproviding a plurality of classification events separated by mark events,with the information provided by the number of classification events.The mark events function to define the individual classification events.A class event counter, if supplied, is arranged to count theclassification events and output information regarding the countedclassification events to PD load circuitry 90, thus providing PD loadcircuitry 90 with information regarding the powering ability of the PSEs60.

Each PSE 60 is further arranged, in the event that sufficient power isavailable to support the power requirements detected and output byclassification functionality 64, to provide operating power for PD 40over the respective associated set of twisted wire pairs 30 ofstructured cable 35 by raising the voltage above the classificationvoltage range responsive to powering functionality 66. First and seconddiode bridges 65 are each arranged to ensure that power received by PDinterface 70 and PD load circuitry 90 is at a predetermined polarityirrespective of the connection polarity of PSE 60. UVLO circuit 100 isarranged to maintain isolation between PSE 60 and PD load circuitry 90until a predetermined operating voltage has been achieved across PDinterface 70, and upon sensing the predetermined operating voltage UVLOcircuit 100 is further arranged to assert output PG thus closingelectronically controlled switch 80 thereby providing power to PD loadcircuitry 90. Optionally, a timer (not shown) may be provided to ensurethat the startup phase is complete prior to closing electronicallycontrolled switch 80.

The current provided to PD 40 by each PSE 60 flows back through senseresistor RS on the return path. Powering functionality 66 is arranged toenable current flow through NMOSFET CL responsive to master control 63and detect the magnitude of the current flowing through sense resistorRS. In the event that the detected current magnitude is greater than, orequal to, the predetermined current value, powering functionality 66 isarranged to reduce the gate voltage of NMOSFET CL, thereby preventingthe magnitude of the current flowing therethrough from exceeding thepredetermined current value. Thus, powering functionality 66 controlsthe power provided to PD 40 according to the detected class thereof. MPSdetection functionality 68 is arranged to monitor the current flowthrough sense resistor RS and to instruct control circuitry 61 to openNMOSFET CL in the event that the current falls below a predeterminedminimum over a predetermined time window, thus ending the poweringcycle.

FIG. 1C illustrates a high level block diagram of a PoE poweringarrangement 200, according to the prior art, which is in all respectsidentical PoE powering arrangement 10 with the exception that a firstand a second PD interface 70 are provided, first PD interface 70 isconnected so as to presented to first PSE 60 in accordance with ALT-Apowering and second PD interface 70 is connected so as to presented tosecond PSE 60 in accordance with ALT-B powering. The outputs of firstand second PD interface 70, after the respective electronicallycontrolled switch 80 are shown as being connected together, however thatis not meant to be limiting in any way, and PD load circuitry 90 may bearranged to accept connections from each of first and second PDinterfaces 70 without exceeding the scope.

First and second PSE 60 are each further arranged to monitor the powerbeing drawn from PD 40. In the event that the amount of current beingdrawn is less than a predetermined maintain power signature (MPS)threshold for a predetermined time period, the respective PSE 60 isarranged to shut down the power because it is determined that PD 40 isshut off, or disconnected. However, when PD 40 is drawing a current,half the current is drawn over the ALT-A twisted wire pairs and half isdrawn over the ALT-B twisted wire pairs. If the drawn current is small,the drawn halves will be very close to the MPS threshold. If there is animbalance between ALT-A and ALT-B, such as one caused by differentvoltage drops of diode bridges 65, one of the portions of drawn currentwill be less than half, thereby dropping below the MPS threshold. As aresult, the respective PSE 60 will shut down the power on the respectiveone of ALT-A and ALT-B even though PD 40 is not shut down, ordisconnected.

SUMMARY OF THE INVENTION

Accordingly, it is a principal object of the present invention toovercome at least some of the disadvantages of prior art poweringarrangements and PSE control. This is accomplished in one embodiment bya power over Ethernet (PoE) power monitoring arrangement for monitoringpower delivered to a powered device over communication cabling, thearrangement comprising: a control circuitry; a first power sourcingequipment (PSE) responsive to the control circuitry, the first PSEcomprising: a first output port arranged for connecting to the powereddevice over a first set of wires; a first power enable circuit; and afirst maintain power signature (MPS) functionality arranged to comparethe current drawn from the first power enable circuit to a firstundercurrent threshold, and disable the first power enable circuit inthe event that the current drawn from the first power enable circuitover a predetermined window is less than the first undercurrentthreshold, a second PSE responsive to the control circuitry, the secondPSE comprising: a second output port arranged for connecting to thepowered device over a second set of wires; a second power enablecircuit; and a second MPS functionality arranged to compare the currentdrawn from the second power enable circuit to a second undercurrentthreshold, and disable the second power enable circuit in the event thatthe current drawn from the second power enable circuit over apredetermined window is less than the second undercurrent threshold, thecontrol circuitry arranged to: receive an indication that the powereddevice presents a single powered device interface to both the first andthe second PSE; and control one of the first and second MPSfunctionality responsive to the received indication.

Additional features and advantages of the invention will become apparentfrom the following drawings and description.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention and to show how the same maybe carried into effect, reference will now be made, purely by way ofexample, to the accompanying drawings in which like numerals designatecorresponding sections or elements throughout.

With specific reference now to the drawings in detail, it is stressedthat the particulars shown are by way of example and for purposes ofillustrative discussion of the preferred embodiments of the presentinvention only, and are presented in the cause of providing what isbelieved to be the most useful and readily understood description of theprinciples and conceptual aspects of the invention. In this regard, noattempt is made to show structural details of the invention in moredetail than is necessary for a fundamental understanding of theinvention, the description taken with the drawings making apparent tothose skilled in the art how the several forms of the invention may beembodied in practice. In the accompanying drawings:

FIG. 1A illustrates a high level block diagram of a first PoE poweringarrangement known to the prior art;

FIG. 1B illustrates a high level block diagram of an embodiment of a PSEknown to the prior art;

FIG. 1C illustrates a high level block diagram of a second PoE poweringarrangement known to the prior art;

FIG. 2A illustrates a high level block diagram of a PSE arrangement,according to certain embodiments;

FIG. 2B illustrates a high level flow chart of a first method of PoEconnection check, according to certain embodiments;

FIGS. 2C-2D illustrate various embodiments of the PSE arrangement ofFIG. 2A, according to certain embodiments;

FIG. 3 FIG. 2B illustrates a high level flow chart of a second method ofPoE connection check, according to certain embodiments;

FIG. 4A illustrates a high level flow chart of a first method of PoEpower monitoring, according to certain embodiments;

FIG. 4B illustrates a high level flow chart of a second method of PoEpower monitoring, according to certain embodiments;

FIG. 5A illustrates a high level block diagram of a PoE power monitoringarrangement, according to certain embodiment; and

FIG. 5B illustrates a high level flow chart of a PoE power monitoringmethod, according to certain embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not limited in its applicationto the details of construction and the arrangement of the components setforth in the following description or illustrated in the drawings. Theinvention is applicable to other embodiments or of being practiced orcarried out in various ways. Also, it is to be understood that thephraseology and terminology employed herein is for the purpose ofdescription and should not be regarded as limiting.

The invention is being described as an Ethernet based network, with apowered device being connected thereto. It is to be understood that thepowered device is preferably an IEEE 802.3 compliant device preferablyemploying a 10Base-T, 100Base-T or 1000Base-T connection.

FIG. 2A illustrates a high level block diagram of a PSE arrangement 300and FIG. 2B illustrates a high level block diagram of a first method ofPoE detection. The method of FIG. 2B is described below as beingimplemented by PSE arrangement 300, however this is not meant to belimiting in any way. FIG. 2C illustrates the connection of PSEarrangement 300 in PoE powering arrangement 10, and FIG. 2D illustratesthe connection of PSE arrangement 300 in PoE powering arrangement 200,FIGS. 2A-2D being described together. PSE arrangement 300 comprises: afirst PSE 310; a second PSE 320; and a control circuitry 330. Forsimplicity only detection functionality 62 of each PSE 320, 330 isillustrated. First PSE 310 comprises: a pair of first outputs 340; arespective detection functionality 62 comprising a first detection powersource 350 and a first power attribute detector 360; and a power enablecircuit 370. Second PSE 320 comprises: a pair of second outputs 380; arespective detection functionality 62 comprising a second detectionpower source 390 and a second power attribute detector 400; and a powerenable circuit 410. Power enable circuits 370, 410 each represent arespective powering functionality 66 in cooperation with current limiterCL and sense resistor RS and classification functionality 64. In oneembodiment, as illustrated in FIGS. 2C-2D, first detection power source350 and second detection power source 390 each comprises a currentsource. Additionally, first power attribute detector 360 and secondpower attribute detector 400 each comprise a voltage detector, denoted440 and 450 respectively, in parallel with a resistor RD. In anotherembodiment, first detection power source 350 and second detection powersource 390 each comprise a voltage source and in such an embodimentfirst power attribute detector 360 and second power attribute detector400 each comprises a current magnitude detector. In one furtherembodiment, the current magnitude detector comprises a voltage detectorarranged to detect the voltage drop across a sense resistor. Each offirst detection power source 350, first power attribute detector 360,second detection power source 390, second detection power source 390 andthe respective power enable circuit 370, 410 are in communication withcontrol circuitry 330, and responsive thereto, the connections not shownfor simplicity. Control circuitry 330 may be implanted as master control63, or a combination of a local control circuit in communication withmaster control 63 without exceeding the scope.

The output of first detection power source 350 is coupled to a first ofpair of first outputs 340, the output denoted OUT1, and the return offirst detection power source 350 is coupled to the second of pair offirst outputs 340. First power attribute detector 360 is coupled to theoutput of first detection power source 350. The output of power enablecircuit 370 is coupled to first output 340 and an input of power enablecircuit 370 is coupled to a power line 420, optionally coupled to anexternal power source (not shown). In one embodiment, the output ofpower enable circuit 370 is directly coupled to power line 420 andNMOSFET CL and sense resistive element RS are coupled with a return line430 of the external power source, return line 430 coupled to secondoutput 340 as described above in relation to FIG. 1B.

The output of second detection power source 390 is coupled to a first ofpair of second outputs 380, the output denoted OUT2, and the return ofsecond detection power source 390 is coupled to the second of pair ofsecond outputs 380. Second power attribute detector 400 is coupled tothe output of second detection power source 390. The output of powerenable circuit 410 is coupled to first output 380 and an input of powerenable circuit 410 is coupled to power line 420. In one embodiment, theoutput of power enable circuit 410 is directly coupled to power line 420and NMOSFET CL and sense resistive element RS are coupled with returnline 430 as described above in relation to FIG. 1B.

Each of outputs 340 of first PSE 310 and outputs 380 of second PSE 320is coupled to the secondary winding of a respective data transformer 50(not shown) for connection over a respective set of wires to PD 40.Particularly, as described above in relation to PoE poweringarrangements 10, 200 each data transformer 50 is coupled to a respectiveone of four twisted wire pairs, a pair of data transformers 50 coupledto the twisted wire pairs of ALT-A and a pair of data transformers 50coupled to the twisted wire pairs of ALT-B. Outputs 340 of first PSE 310are coupled to a first pair of data transformers 50 and outputs 380 ofsecond PSE 320 are coupled to a second pair of data transformers 50.

In operation, in stage 1000 control circuitry 330 is arranged to controlfirst detection power source 350 to generate a first detection power fora first predetermined time period. As described above, in one embodimentfirst detection power source 350 comprises a current source. In such anembodiment, the generated first detection power comprises a currentexhibiting a predetermined magnitude. In another embodiment, asdescribed above, first detection power source 350 comprises a voltagesource. In such an embodiment, the generated first detection powercomprises a voltage exhibiting a predetermined value. In one embodiment,the generated first detection power is in accordance with therequirements of IEEE 802.3af-2003, IEEE 802.3at-2009 and/or HDBaseTSpecification Version 1.1.0, however this is not meant to be limiting inany way. Additionally, control circuitry 330 is arranged to controlsecond detection power source 390 to not generate a detection powerduring the first predetermined time period.

The generated first detection power is output at outputs 340 of PSE 310and is thus output over the respective twisted wire pairs. In the eventthat a PD is not coupled to the twisted wire pairs, the generated firstdetection power will not be output from PSE 310 and the entirety thereofwill be detected by first power attribute detector 360. In the eventthat a PS is coupled to the twisted wire pairs, the generated firstdetection power will be split between first PSE 310 and the signatureresistance of the PD. For example, in the embodiment where firstdetection power source 350 is a current source and first power attributedetector 360 comprises a respective voltage detector 440, 450, inparallel with a resistor RD, as illustrated in FIGS. 2C-2D, a firstportion I11 of the generated current will flow through resistor RD offirst power attribute detector 360 and a second portion I12 of thegenerated current will flow through signature resistance RSIG of the PD,thereby presenting a smaller voltage across resistor RD of first powerattribute detector 360 than when no PD is present.

In stage 1010, during the first time period of stage 1000, i.e. when thegenerated first detection power is output at output OUT1 of firstdetection power source 350, control circuitry 330 is arranged to obtainfrom first power attribute detector 360 an indication of a first powerattribute being delivered over the first set of wires. Optionally, thefirst power attribute is detected by first power attribute detector 360at the output of first detection power source 350. Particularly, in theembodiment that first power attribute detector 360 comprises voltagedetector 440 in parallel with resistor RD, the first power attribute isthe value of the voltage across resistor RD generated by first portionI11 of the current output from first detection power source 350. Asdescribed above, in the event that a PD is not present, the entirety ofthe current output from first detection power source 350 flows throughresistor RD of first power attribute detector 360. Optionally, thedetection phase described above in relation to PoE arrangements 10 and200 is performed and only in the event that a valid signature resistanceis detected will stages 1010-1050 performed, as will be describedfurther below.

In stage 1020, control circuitry 330 is arranged to control seconddetection power source 390 to generate a second detection power for asecond predetermined time period. The first time period of stage 1000 isdescribed herein as preceding the second time period of stage 1020,however this is not meant to be limiting in any way. In anotherembodiment, the generation of the second detection power, and subsequentstages described below, precede the generation of the first detectionpower of stage 1000, without exceeding the scope. During the secondpredetermined time period, control circuitry 330 is arranged to controlfirst detection power source 350 to continue to generate the firstdetection power of stage 1000.

The generated second detection power is arranged to be greater than thegenerated first detection power of stage 100 by at least a predeterminedamount. Particularly, in the embodiment where first detection powersource 350 and second detection power source 390 each comprise a currentsource, as illustrated in FIGS. 2C-2D, optionally the magnitude of thecurrent generated by second detection power source 390 is greater thanthe current generated by first detection power source 350 so as to besufficient to be detected at the first set of wires. Alternatively, thevalues of the resistance values of resistors RD of first power attributedetector 360 and second power attribute detector 400 are arranged suchthat the voltage output at outputs 380 of second PSE 320 responsive tosecond detection power source 390 is greater than the voltage output atoutputs 340 of first PSE 310 responsive to first detection power source350 by a predetermined value, optionally at least 0.7 volts. In theembodiment wherein first detection power source 350 and second detectionpower source 390 each comprise a voltage source, the value of thevoltage output by second detection power source 390 is arranged to begreater than the value of the voltage output by first detection powersource 350 by a predetermined value, optionally at least 0.7 volts.

In one embodiment, the generated second detection power is in accordancewith the requirements of IEEE 802.3af-2003, IEEE 802.3at-2009 and/orHDBaseT Specification Version 1.1.0, however this is not meant to belimiting in any way.

The generated second detection power is output at outputs 380 of PSE 320and the generated first detection power is output at outputs 340 of PSE310. The generated first and second detection powers are each thusoutput over the respective twisted wire pair sets. As described above inrelation to PoE powering arrangement 10, in the event that a high powerPD with a single PD interface 70 is coupled to the four twisted wirepairs, a diode bridge 65 will be presented to each of PSE 310, 320, theterminals of diode bridges 65 coupled to each other. As a result, theoutput second detection power of second PSE 320 will be presented at theoutput of diode bridge 65 associated with first PSE 310. Since thecurrent, or voltage, of the second detection power is greater than thecurrent, or voltage, of the first detection power, current will not flowfrom first PSE 310 to the respective diode bridge 65 because of thehigher current, or voltage, blocking the output of the diode bridge 65.Particularly, in the embodiment illustrated in FIG. 2C, current portionI11 is less than current portion I21, thereby generating a smallervoltage across the respective resistor RD. The voltage generated bycurrent portion I22 across signature resistance RSIG is greater than thevoltage across resistor RD of first power attribute detector 360,thereby blocking current portion I12 from flowing towards the respectivediode bridge 65. As a result, current portion I12 is added to currentportion I11 flowing through resistor RD, thereby increasing the voltagethereacross. First detection power source 350 and second detection powersource 390 are arranged such that the voltage across the respectiveresistor RD generated responsive to current portions I11 and I12 flowingtherethrough is less than, or less than a voltage drop greater than, thevoltage across signature resistance RSIG generated responsive to currentportion I22 flowing therethrough.

In the event that a separate PD is presented to each of PSEs 310, 320,as illustrated in FIG. 2D, the current output by second detection powersource 390 will have no effect on the current output by first detectionpower source 350. In such an event, current portion I12 will flowthrough the respective signature resistance RSIG and current portion I22will flow through the respective signature resistance RSIG.

In stage 1030, during the second predetermined time period of stage1020, i.e. when the generated first detection power is output at outputOUT1 of first detection power source 350 and the generated seconddetection power is output at output OUT2 of second detection powersource 390, control circuitry 330 is arranged to obtain from first powerattribute detector 360 an indication of a second power attribute overthe first set of wires. Particularly, in the embodiment that first powerattribute detector 360 comprises voltage source 440 in parallel with therespective resistor RD, as illustrated in FIGS. 2C-2D, the second powerattribute is the value of the voltage across resistor RD generated bythe current flowing therethrough. As described above, in the event thata single PD interface 70 is present and coupled across four twisted wirepairs, as illustrated in FIG. 2C, the voltage across resistor RD offirst power attribute detector 360 is generated by portions I11 and I12of the current output from first detection power source 350. In theevent that a separate PD interface 70 is presented to each of first andsecond PSEs 310, 320, as illustrated in FIG. 2D, the voltage acrossresistor RD of first power attribute detector 360 is generated only bycurrent portion I11, as current portion I12 flows through the respectivediode bridge 65 and signature resistance RSIG.

In stage 1040, control circuitry 330 is arranged to determine thedifference between the received second power attribute indication ofstage 1030 and the received first power attribute indication of stage1010, the difference denoted the first difference. Optionally, thedifference is determined as an absolute value.

As described further below, in certain embodiment control circuitry 330is further arranged to compare the determined difference with apredetermined threshold. In the event that the determined difference isgreater than the predetermined threshold, it is determined that a singlePD interface 70 is connected over the four twisted wire pairs since thedifference is caused by the effect of second PSE 320 on first PSE 310,i.e. there is a connection between them. In the event that thedetermined difference is not greater than the predetermined threshold,it is determined that separate PD interfaces 70 are connected over thetwisted wire pairs since second PSE 320 does not affect first PSE 310.

In general the difference with between the first power attribute ofstage 1010 and the second power attribute of stage 1030 is indicative asto whether a single PD interface 70 is presented by PD 40 or a pair ofPD interfaces 70 are presented by PD 40.

In stage 1050, control circuitry 330 is arranged to control power enablecircuit 370 to enable a first supply power and to control power enablecircuit 410 to enable a second supply power. In one embodiment, asdescribed above, the power enable circuit 370 comprises poweringfunctionality 66 arranged to control an associated NMOSFET CL coupledbetween return line 430 and the respective one of outputs 340, 380. Inanother embodiment, power enable circuit 370 comprises poweringfunctionality 66 arranged to control an associated current limitercoupled between power line 420 and the respective one of outputs 340,380. Additionally, at least one of power enable circuit 370 and powerenable circuit 410 are controlled in accordance with the determinedfirst difference of stage 1040. In the event that it is determined instage 1040 that a single PD interface 70 is connected to the fourtwisted wire pairs, optionally detection is performed only by one offirst and second PSEs 310 and 320, as described above. As describedabove, in the event that it is determined in stage 1040 that two PDinterfaces 70 are connected to the four twisted wire pairs, detection isperformed by second PSE 320, in addition to the detection performed byfirst PSE 310.

In one embodiment, the control of stage 1050 comprises control of theclassification stage. As described above in relation to PoE poweringarrangement 10, optionally first and second PSEs 310 and 320 eachcomprise a classification functionality 64 arranged to determine theclass of the PD interface 70 connected thereto, the classificationfunctionality part of the respective power enable circuitry 370, 410. Inthe event that it is determined that a separate PD interface 70 isconnected to each of first and second PSEs 310 and 320, classificationis performed separately for each PD interface 70 and control circuitry330 controls powering functionalities 62 of first and second PSE 310,320 accordingly. Particularly, control circuitry 330 is arranged todetermine if enough power is available to supply the requirements of theparticular class of the PD interface 70 and only if enough power isavailable will the first and second supply powers by supplied. In theevent that only a single PD interface is coupled over the four twistedwire pairs, classification is performed for the single PD interface 70as a high powered device and the first and second supply powers aresupplied responsive to the classification. Optionally, classificationfor a single high powered PD interface 70 is performed as described inU.S. Patent Application Publication S/N 2013/0257161 published Oct. 3,2013, the entire contents of which is incorporated herein by reference.

In another embodiment, as will be described below in relation to FIGS.4A-4B, in the event that a single PD interface 70 is determined to beconnected and an imbalance is detected between ALT-A and ALT-B, a MPSfunctionality 68 is disabled at one of PSEs 310 and 320 by controlcircuitry 330. As a result, the supply power of the one of PSEs 310 and320 whose MPS is disabled is still provided even if the power drawntherefrom by the PD is less than the MPS threshold.

Control circuitry 330 may be further arranged to utilize stage 1000 aspart of a detection scheme, and as such since only a single level wasgenerated in stage 1000, control circuitry 330 may enable at least oneadditional detection power from first detection power source 350 andreceive from first power attribute detector 360 an indication of arespective power attribute at output OUT1 of first detection powersource 350, in the absence of any output from second detection powersource 390. Detection of a valid PD typically requires separatelyoutputting two levels of detection power and detecting the powerattribute for each power level. This allows for accurate measurement ofsignature resistance RSIG even though diode bridge 65 has an unknowneffect on the measurement, since the effect of diode bridge 65 isconstant between the two impressed power levels. Particularly, in theevent that control circuitry 330 determines in stage 1040 that only asingle PD interface 70 is coupled to the four twisted wire pairs, the PDis validated responsive to the detected first power attribute and anadditional power attribute as described. Similarly, a plurality oflevels are provided solely by second detection power source 390 and therespective associated power attributes obtained from second powerattribute detector 400.

In one alternative embodiment, detection of a valid PD interface 70 isperformed separately by each of first and second PSEs 310 and 320 priorto stages 1000-1050. In such an embodiment, only in the event that bothfirst and second PSEs 310 and 320 detect a valid signature resistanceRSIG are stages 1000-1050 performed. In another alternative embodiment,the detection stage is performed after the determination in stage 1050if one or two PD interfaces 70 are connected. In the event that a singlePD interface 70 is detected as connected, detection is performed by oneof first PSE 310 and second PSE 320. In the event that two PD interfaces70 are detected as connected, detection is performed by each of firstand second PSEs 310 and 320 for the respective PD interface 70.

FIG. 3 illustrates a high level flow chart of a second method of PoEdetection. The method of FIG. 3 is described as being implemented by PSEarrangement 300 of FIG. 2A, however this is not meant to be limiting inany way. In stage 2000, control circuitry 330 is arranged to controlfirst detection power source 350 to generate a first detection power fora first predetermined time period and additionally control seconddetection power source 390 to not generate a second detection power, asdescribed above in relation to stage 1000. In stage 2010, during thefirst time period of stage 2000, i.e. when the generated first detectionpower is output at output OUT1 of first detection power source 350,control circuitry 330 is arranged to obtain from first power attributedetector 360 an indication of a first power attribute over the first setof wires, optionally at the output of first detection power source 350,as described above in relation to stage 1010. Additionally, controlcircuitry 330 is arranged to receive from second power attributedetector 400 an indication of a third power attribute over the secondset of wires, optionally at the output of second detection power source360.

In stage 2020, control circuitry 330 is arranged to control seconddetection power source 390 to generate a second detection power for asecond predetermined time period. As described above, the first timeperiod of stage 2000 is described herein as preceding the second timeperiod of stage 2020, however this is not meant to be limiting in anyway. During the second predetermined time period, control circuitry 330is arranged to control first detection power source 350 to continue togenerate the first detection power of stage 2000. As described above,the generated second detection power is greater than the generated firstdetection power of stage 2000.

In stage 2030, during the second time period of stage 2020, i.e. whenthe generated first detection power is output at output OUT1 of firstdetection power source 350 and the generated second detection power isoutput at output OUT2 of second detection power source 390, controlcircuitry 330 is arranged to obtain from first power attribute detector360 an indication of a second power attribute indication over the firstset of wires, optionally at the output of first detection power source350, as described above in relation to stage 1010. Additionally, controlcircuitry 330 is arranged to receive from second power attributedetector 400 an indication of a fourth power attribute over the secondset of wires, optionally at the output of second detection power source360.

In stage 2040, control circuitry 330 is arranged to determine the firstdifference between the received indication of the detected second powerattribute at OUT1 of stage 2030 and the received indication of thedetected first power attribute at OUT1 of stage 2010 as a firstdifference. In stage 2050, control circuitry 330 is arranged todetermine the difference between the received indication of the detectedfourth power attribute at OUT2 of stage 2030 and the received indicationof the detected third power attribute at OUT2 of stage 2010 as a seconddifference.

In stage 2060 control circuitry 330 is further arranged to compare thedetermined first difference of stage 2040 with a first predeterminedthreshold and the determined second difference of stage 2050 with secondpredetermined threshold. In the event that the determined first andsecond differences are each greater than the respective one of the firstand second predetermined thresholds, it is determined that a single PDinterface 70 is connected over the four twisted wire pairs and stage2070 is performed, as described below. As described above, thedifference between the second power attribute and the first powerattribute at OUT1 is caused by the effect of PSE 320 on PSE 310.Additionally, the third power attribute of stage 2010 should be zero,since no detection power is being output by second detection powersource 390, and therefore there should be a significant differencebetween the third power attribute of stage 2010 and the fourth powerattribute of stage 1030. A smaller difference, or no difference, wouldindicate that a short circuit exists which supplies power to secondpower attribute detector 400 from first detection power source 350. Instage 2070, control circuitry 330 is arranged to control first powerenable circuit 370 and second power enable circuit 410 to each provide arespective supply power, in accordance with the determination that asingle PD interface 70 is coupled to the four twisted wire pairs, asdescribed above. Optionally, this includes only performingclassification by one of first PSE 310 and second PSE 320.

In the event that in stage 2060 the first and second differences are notgreater than the respective thresholds, in stage 2080 control circuitry330 is arranged to determine whether the first determined difference isless than a third predetermined threshold, the third predeterminedthreshold less than the first predetermined threshold of stage 2060. Inthe event that the first determined difference is less than the thirdpredetermined threshold, and the second determined difference is greaterthan the second predetermined threshold of stage 2060, as performedtherein, in stage 2090 control circuitry 330 is arranged to controlfirst power enable circuit 370 and second power enable circuit 410 toeach provide a respective supply power, in accordance with thedetermination that a separate PD interface 70 is coupled to each ofALT-A and ALT-B. Optionally, this entails each of first power enablecircuit 370 and second power enable circuit 410 performingclassification Particularly, in the event that a separate PD interfaceis coupled to each of ALT-A and ALT-B, as described above in relation toFIG. 2D, there should be no significant difference between the firstpower attribute and the second power attribute since nothing shouldaffect the detection. A significant difference between the first powerattribute and the second power attribute would indicate that a shortcircuit exists which supplies power to first power attribute detector360 from second detection power supply 390.

In the event that in stage 2080 the determined first difference is notless than the third threshold, and/or the second difference is notgreater than the second threshold, in stage 2100 control circuitry 330is arranged to control first power enable circuit 370 and second powerenable circuit 410 to not provide the respective first supply power andsecond supply power. In one embodiment, control circuitry 330 is furtherarranged to output an error signal.

FIG. 4A illustrates a high level flow chart of a first method of PoEpower monitoring performed by master control 63 of powering arrangements10, 200. The method of FIG. 4A is described herein as being implementedby master control 63 of powering arrangements 10, 200, however this isnot meant to be limiting in any way. In stage 3000, master control 63,or control circuitry 330, is arranged to determine whether 1 or 2 PDinterfaces 70 are coupled to twisted wire pairs 30, as described abovein relation to stages 1000-1050 of FIG. 2B and stages 2000-2080 of FIG.3. In stage 3010, first and second PSEs 310 and 320 are arranged todetect a valid signature resistance of the 1 or 2 PD interfaces 70connected to twisted wire pairs 30. As described above, in the eventthat only a single PD interface 70 is connected to twisted wire pairs 30the detection may be performed by only one of first and second PSEs 310and 320. In optional stage 3020, first and second PSEs 310 and 320 arearranged to perform classification of the 1 or 2 PD interfaces 70. Inthe event that 2 PD interfaces 70 are connected to twisted wire pairs30, classification is performed as described above in relation toclassification functionality 64. In the event that a single PD interface70 is connected to twisted wire pairs 30, classification is performed byonly a single one of first and second PSE 310, 320. In stage 3030, firstand second PSE 310 and 320 are arranged to supply power over the fourtwisted wire pairs 30, as described above in relation to stage 1080.

In stage 3040, as described above in relation to stage 3000, controlcircuitry 330 is arranged to determine whether 1 or 2 PD interfaces 70are connected to twisted wire pairs 30. In the event that controlcircuitry 330 determines that a single PD interface 70 is connected totwisted wire pairs 30, in stage 3050 control circuitry 330 is arrangedto detect an imbalance between ALT-A and ALT-B. Particularly, asdescribed above, the primary winding of each data transformer 50 of PD40 is coupled to a respective one of pair of diode bridges 65. When asingle PD interface 70 is coupled to twisted wire pairs 30, half thepower drawn thereby is provided over ALT-A by first PSE 310 and theother half is provided over ALT-B by second PSE 320. The voltage drop ofthe diodes of diode bridges 65 are not exactly equal to each other,thereby causing an imbalance between the power provided over ALT-A andthe power provided over ALT-B, i.e. the power provided over ALT-B is notexactly equal to the power provided over ALT-A. As described above,power is provided to PD circuitry 90 by the respective supply powersources 370 and 410 of first and second PSEs 310 and 320. As known tothose skilled in the art at the time of the invention, PSEs 310 and 320are each arrangement to monitor the power being provided thereby by arespective MPS functionality 68. In the event that less than apredetermined amount of power is being drawn from the respective PSEover a predetermined time window, MPS functionality is in communicationwith the powering functionality 66 to disconnect the power beingprovided to PD interface 70.

In optional stage 3060, the current flowing through twisted wire pairs30 of ALT-A is measured by first PSE 310 and the current flowing throughtwisted wire pairs 30 of ALT-B is measured by second PSE 320. Controlcircuitry 330 is arranged to compare the measured current of ALT-A withthe measured current of ALT-B and determine the difference therebetween.In optional stage 3070, the voltage at the output of first PSE 310 ismeasured by first PSE 310 and the voltage at the output of second PSE320 is measured by second PSE 320. Control circuitry 330 is arranged tocompare the measured voltage at the output of first PSE 310 with themeasured voltage at the output of second PSE 320 and determine thedifference therebetween. In stage 3080, control circuitry 330 isarranged compare the detected imbalance of stage 3050 to a predeterminedimbalance threshold. In one embodiment, control circuitry 330 isarranged to compare the current difference of optional stage 1060 withthe predetermined imbalance threshold. In another embodiment, controlcircuitry 330 is arranged to compare the voltage difference of optionalstage 1070 with the predetermined imbalance threshold. In the event thatthe determined imbalance is greater than the predetermined threshold,control circuitry 330 is arranged to disable the MPS monitoring of theone of first and second PSEs 310, 320 associated with the diode bridge65 exhibiting the lower voltage drop, i.e. the PSE exhibiting the lowercurrent of optional stage 3060 or the higher voltage of optional stage3070. If PD circuitry 90 draws a low current during operation, the lowcurrent is split between ALT-A and ALT-B, as described above. Due to theimbalance between ALT-A and ALT-B, the current associated with the diodebridge 65 exhibiting the lower voltage drop may be smaller than the MPSthreshold and the respective one of PSEs 310 and 320 will shut down thepower responsive to the respective MPS functionality 68. Advantageously,disabling the respective MPS functionality of the respective one offirst and second PSEs 310, 320 avoids this problem. Since only a singlePD interface 70 is connected to twisted wire pairs 30, the MPS needs tobe monitored only on one of ALT-A and ALT-B.

In the event that in stage 3080 the detected imbalance of stage 3050 isless than the predetermined imbalance threshold, or in the event that instage 3040 a pair of PD interfaces 70 are connected to twisted wirepairs 30, stage 3000 described above is again performed.

In an alternative embodiment, the MPS counter of each of first PSE 310and second PSE 320 are monitored, the counter tracking time in thepredetermined window for which under-current is detected. In the eventthat master control 63 notes that one counter is advancing and the otheris not, master control 63 disabled the MPS functionality 68 of the PSEwhose counter has been advancing. Thus, only the undisabled MPSfunctionality is operative. Optionally, the disabled MPS functionality68 is again enabled in the event that the port current is detected asexceeding a pre-existing value, or a disconnect was actually detected,followed by a reconnect.

In an alternative embodiment, in stage 3090, the MPS threshold of one ormore of the MPS functionalities 68 are reduced responsive to theimbalance. The reduction may be performed in steps of a predeterminedsize, or may be done responsive to the level of imbalance detected instage 3050.

FIG. 4B illustrates a high level flow chart of a second method of PoEpower monitoring. The method of FIG. 4B is described as beingimplemented by PoE powering arrangements 10, 200, however this is notmeant to be limiting in any way. In stage 4000, control circuitry 330 isarranged to determine whether 1 or 2 PD interfaces 70 are coupled totwisted wire pairs 30, as described above in relation to stages1000-1060 of FIG. 2B. In stage 4010, first and second PSEs 310, 320 arearranged to detect a valid signature resistance of the 1 or 2 PDinterfaces 70 connected to twisted wire pairs 30. As described above, inthe event that only a single PD interface 70 is connected to twistedwire pairs 30 the detection may be performed by only one of first andsecond PSEs 310 and 320. In optional stage 4020, PSEs 310 and 320 arearranged to perform classification of the 1 or 2 PD interfaces 70. Inthe event that 2 PD interfaces 70 are detected as connected to twistedwire pairs 30, classification is performed as described above inrelation to classification functionality 64. In the event that a singlePD interface 70 is connected to twisted wire pairs 30, classification ifperformed as described above in relation to stage 1080 of FIG. 2B. Instage 4030, first and second PSEs 310 and 320 are arranged to supplypower over the four twisted wire pairs 30, as described above inrelation to stage 1080.

In stage 4040, as described above in relation to stage 4000, controlcircuitry 330 is arranged to determine whether 1 or 2 PD interfaces 70are connected to twisted wire pairs 30. In the event that controlcircuitry 330 determines that a single PD interface 70 is connected totwisted wire pairs 30, in stage 4050 control circuitry 330 is arrangedto monitor the sum of the power output on ALT-A and the sum of poweroutput on ALT-B. As described above in relation to stage 3050, first andsecond PSEs 310 and 320 are each arranged to monitor the amount of powerbeing drawn by PD interface 70. Control circuitry 330 is arranged to sumthe monitored powers of each of first and second PSE 310 and 520 andcompare the summed powers to a predetermined MPS threshold, controlcircuitry 330 further arranged to control PSEs 310 and 320 to disablethe power being supplied to PD interface 70 in the event that the sum ofthe powers on ALT-A and ALT-B is less than the predetermined MPSthreshold. Advantageously, an imbalance between ALT-A and ALT-B,described above, won't affect the power monitoring because the sum ofpowers of ALT-A and ALT-B is being monitored. MPS functionality of eachof first and second PSE 30, 320 is preferably disabled.

In the event that in stage 4040 control circuitry 530 determines that aseparate PD interface 70 is coupled over each of ALT-A and ALT-B, firstand second PSEs 310 m 320 are each arranged to monitor the powersupplied to the respective PD interface 70 via their respective MPSfunctionality 68 and shut down the power being supplied if the monitoredpower is less than a respective MPS threshold, as known to those skilledin the art at the time of the invention.

FIG. 5A illustrates a high level block diagram of PoE power monitoringarrangement 600. FIG. 5B illustrates a high level flow chart of a PoEpower monitoring method. The PoE power monitoring method of FIG. 5B isdescribed as being implemented by PoE power monitoring arrangement 600of FIG. 5A, however this is not meant to be limiting in any way. PoEpower monitoring arrangement 600 comprises: a first PSE 610; a secondPSE 620; and a control circuitry 630. First PSE 610 comprises: a pair ofoutputs 340; a power enable circuit 370; an MPS functionality 640; andan optional power attribute detector 650. Second PSE 620 comprises: apair of outputs 380; a power enable circuit 410; an MPS functionality640; and an optional power attribute detector 650. MPS functionality 640of each of first PSE 610 and second PSE 620 may be constituted in adedicated circuitry, or as a programmed functionality for a computingelement, without limitation.

MPS functionality 640 of each of first PSE 610 and second PSE 620 iscoupled to a first of the respective pair of outputs 340 and 380, and isfurther coupled to the respective one of supply power sources 370 and410. Optional power attribute detector 650 of each of first PSE 610 andsecond PSE 620 is coupled to the respective pair of outputs 340 and 380.The output of first power enable circuit 370 is coupled to first output340 and an input of first power enable circuit 370 is coupled to a powerline 420, optionally coupled to an external power source (not shown). Inone embodiment, the output of first power enable circuit 370 is directlycoupled to power line 420 and current limiter CL and sense resistiveelement RS are coupled within a return line 430 of the external powersource, return line 430 coupled to second output 340. The output ofsecond power enable circuit 410 is coupled to first output 380 and aninput of second power enable circuit 410 is coupled to power line 410.In one embodiment, the output of second power enable circuit 410 isdirectly coupled to power line 420 and current limiter CL and senseresistive element RS are coupled within return line 430. Controlcircuitry 630 is in communication with each of first power enablecircuit 370, second power enable circuit 410, MPS functionalities 640and optional power attribute detectors 650, the connections not show forsimplicity. First and second PSEs 610, 620 are described as comprising arespective power enable and an MPS functionality, however this is notmeant to be limiting in any way and first and second PSEs 610, 620preferably additionally comprise a detection functionality 62 andoptionally a classification functionality 64, as described above inrelation to PoE powering arrangement 10 of FIG. 1A. As described above,power enable 370, 410 preferably further comprise MPS functionality 640and classification functionality 64.

Each of outputs 340 of first PSE 610 and outputs 380 of second PSE 620is coupled to the secondary winding of a respective data transformer 50(not shown). Particularly, as described above in relation to PoEpowering arrangement 10, each data transformer 50 is coupled to arespective one of four twisted wire pairs, a pair of data transformers50 coupled to the twisted wire pairs of ALT-A and a pair of datatransformers 50 coupled to the twisted wire pairs of ALT-B. Outputs 340of first PSE 610 are coupled to a first pair of data transformers 50 andoutputs 380 of second PSE 620 are coupled to a second pair of datatransformers 50.

In stage 5000, control circuitry 630 is arranged to control first powerenable circuit 370 to provide a first supply power and control secondpower enable circuit 410 to provide a second supply power. As describedabove, the generation of the first and second supply powers are precededby a detection, and optionally a classification, stage. In stage 5010,MPS functionality 640 of each of first PSE 610 and second PSE 620 isarranged to determine a first power attribute of the provided respectiveone of the first supply power and the second supply power. Optionally,the first power attribute comprises one of: a direct current (DC)current magnitude of the respective one of the first supply power andthe second supply power; and an alternating current (AC) impedance valueof the respective one of the first supply power and the second supplypower. It is to be note, that imbalance is not detected by AC impedancedetection.

In stage 5020, for each of first PSE 610 and second PSE 620, responsiveto a first type relationship between the respective first type powerattribute of stage 5010 and a predetermined MPS threshold, therespective MPS functionality 640 is arranged to control the respectiveone first power enable circuit 370 and second power enable circuit 410to cease generation of the respective one of the first supply power andthe second supply power. Optionally, in the embodiment where the firstpower attribute comprises a DC current magnitude, the first typerelationship comprises the DC current magnitude being less than apredetermined MPS DC current magnitude threshold over a predeterminedtime period.

In stage 5030, for each of first PSE 610 and second PSE 620, responsiveto a second type relationship between the respective first type powerattribute of stage 5010 and the predetermined MPS threshold of stage5020, the respective MPS functionality 640 is arranged to control therespective one first power enable circuit 370 and second power enablecircuit 410 to maintain the generation of the respective one of thefirst supply power and the second supply power. Optionally, in theembodiment where the first power attribute comprises a DC currentmagnitude, the second type relationship comprises the DC currentmagnitude being greater than, or equal to, the predetermined MPS DCcurrent magnitude threshold of stage 5020 over the predetermined timeperiod.

In stage 5040, control circuitry 630 is arranged to receive one of asingle PD interface indication and PD interface pair indication. Thesingle PD interface indication is indicative that a single PD interface70 is in electrical communication with pair of first outputs 340 offirst PSE 610 and pair of second outputs 380 of second PSE 620, i.e. asingle PD interface 70 is connected over the four twisted wire pairs.The PD pair indication is indicative that a first PD interface 70 is inelectrical communication with pair of first outputs 340 of first PSE 610and a second PD interface 70 is in electrical communication with pair ofsecond outputs 380 of second PSE 620. In one embodiment, the single PDindication and PD pair indication are each generated in accordance withthe method described above.

In stage 5050, responsive to a received PD interface pair indication ofstage 5040, control circuitry 630 is arranged to allow MPS functionality640 of each of first PSE 610 and second PSE 620 to control therespective one of first power enable circuit 370 and second power enablecircuit 410 to cease generating the respective one of the first supplypower and the second supply power. As described above in relation tostage 5020-5030, MPS functionality 640 is arranged to maintain ordisable the respective supply power responsive to detection of a firstpower attribute of the respective supply power. In stage 5060,responsive to a received single PD interface indication of stage 5040,control circuitry 630 is arranged to not allow MPS functionality 640 ofat least one of first PSE 610 and second PSE 620 to control therespective one of first power enable circuit 370 and second power enablecircuit 410 to cease generating the respective one of the first supplypower and the second supply power, i.e. the disabling function of MPSfunctionality 640.

In optional stage 5070, optional detector 650 of each of first PSE 610and second PSE 620 is arranged to detect a second operating powerattribute of the respective one of the first power enable circuit andthe second power enable circuit. Control circuitry 630 is furtherarranged to compare the detected second operating power attributes.Responsive to the comparison, control circuitry 630 is arranged to notallow a respective one of MPS functionalities 640 to control therespective one of the first provided supply power and second providedsupply power, as described above in relation to stage 5060. Optionally,the second operating power attribute is one of: the current magnitudeflowing through the respective one of outputs 340 and outputs 380, i.e.the same as the first operating power attribute described above; and thevoltage between outputs 340 or outputs 380, i.e. the voltage between thesecondary windings of the respective data transformers 50. Optionally,control circuitry 630 is further arranged to determine the differencebetween the second operating power attribute of first PSE 610 and thesecond operating power attribute of second PSE 620. In the event thatthe determined difference is greater than a predetermined imbalancethreshold, control circuitry 630 is arranged to not allow a respectiveone of MPS functionalities 640 to control the respective one of thefirst provided supply power and second provided supply power, asdescribed above in relation to stage 3090 of FIG. 4A. In the event thatthe determined difference is less than, or equal to, the predeterminedimbalance threshold, control circuitry 630 is arranged to allow both MPSfunctionality 640 to control the respective generated supply powers.

In optional stage 5080, control circuitry 630 is arranged to determine asum of the detected first power attributes of stage 5010. Controlcircuitry 630 is arranged to control first power enable circuit 370 andsecond power enable circuit 410 to cease the provision of the firstsupply power and the second supply power, as described above in relationto stage 4050 of FIG. 4C. Advantageously, any imbalance is compensatedfor by summing the two supply powers together to determine if the PDcircuitry 90 is drawing power. In optional stage 5090, responsive to afirst type relationship between the determined sum of optional stage5080 and a second MPS threshold, control circuitry 630 is arranged tocontrol first power enable circuit 370 and second power enable circuit410 to cease the generation of the first supply power and the secondsupply power. Responsive to a second type relationship between thedetermined sum of optional stage 5080 and the second MPS threshold,control circuitry 630 is arranged to control first power enable circuit370 and second power enable circuit 410 to maintain the generation ofthe first supply power and the second supply power, the second typerelationship opposing the first type relationship. As described above inrelation to stage 5020, optionally in the embodiment where the firstpower attribute comprises a DC current magnitude, the first typerelationship comprises the DC current magnitude being less than apredetermined MPS DC current magnitude threshold over a predeterminedtime period.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable subcombination. In particular, the invention has beendescribed with an identification of each powered device by a class,however this is not meant to be limiting in any way. In an alternativeembodiment, all powered device are treated equally, and thus theidentification of class with its associated power requirements is notrequired.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meanings as are commonly understood by one of ordinaryskill in the art to which this invention belongs. Although methodssimilar or equivalent to those described herein can be used in thepractice or testing of the present invention, suitable methods aredescribed herein.

All publications, patent applications, patents, and other referencesmentioned herein are incorporated by reference in their entirety. Incase of conflict, the patent specification, including definitions, willprevail. In addition, the materials, methods, and examples areillustrative only and not intended to be limiting.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Rather the scope of the present invention isdefined by the appended claims and includes both combinations andsubcombinations of the various features described hereinabove as well asvariations and modifications thereof which would occur to personsskilled in the art upon reading the foregoing description.

The invention claimed is:
 1. A power over Ethernet (PoE) powermonitoring arrangement for monitoring power delivered to a powereddevice over communication cabling, the arrangement comprising: a controlcircuitry; a first power sourcing equipment (PSE) responsive to saidcontrol circuitry, said first PSE comprising: a first output portarranged for connecting to the powered device over a first set of wires;a first power enable circuit; and a first maintain power signature (MPS)functionality arranged to compare the current drawn from said firstpower enable circuit to a first undercurrent threshold, and disable saidfirst power enable circuit in the event that said current drawn fromsaid first power enable circuit over a predetermined window is less thanthe first undercurrent threshold, a second PSE responsive to saidcontrol circuitry, said second PSE comprising: a second output portarranged for connecting to the powered device over a second set ofwires; a second power enable circuit; and a second MPS functionalityarranged to compare the current drawn from said second power enablecircuit to a second undercurrent threshold, and disable said secondpower enable circuit in the event that said current drawn from saidsecond power enable circuit over a predetermined window is less than thesecond undercurrent threshold, said control circuitry arranged to:receive an indication that the powered device presents a single powereddevice interface to both said first and said second PSE; and control oneof said first and second MPS functionality responsive to said receivedindication, wherein said control of one of said first and second MPSfunctionality, comprises: disable both of said first and second MPSfunctionality; monitor the sum of the current drawn from said firstpower enable circuit and the current drawn from said second power enablecircuit; and in the event that the sum of the currents drawn exceeds acombination threshold, disable both said first power enable circuit andsaid second power enable circuit.
 2. A power over Ethernet (PoE) powermonitoring arrangement for monitoring power delivered to a powereddevice over communication cabling, the arrangement comprising: a controlcircuitry; a first power sourcing equipment (PSE) responsive to saidcontrol circuitry, said first PSE comprising: a first output portarranged for connecting to the powered device over a first set of wires;a first power enable circuit; and a first maintain power signature (MPS)functionality arranged to compare the current drawn from said firstpower enable circuit to a first undercurrent threshold, and disable saidfirst power enable circuit in the event that said current drawn fromsaid first power enable circuit over a predetermined window is less thanthe first undercurrent threshold, a second PSE responsive to saidcontrol circuitry, said second PSE comprising: a second output portarranged for connecting to the powered device over a second set ofwires; a second power enable circuit; and a second MPS functionalityarranged to compare the current drawn from said second power enablecircuit to a second undercurrent threshold, and disable said secondpower enable circuit in the event that said current drawn from saidsecond power enable circuit over a predetermined window is less than thesecond undercurrent threshold, said control circuitry arranged to:receive an indication that the powered device presents a single powereddevice interface to both said first and said second PSE; and control oneof said first and second MPS functionality responsive to said receivedindication, wherein said control of one of said first and second MPSfunctionality, comprises: monitor the difference between the currentdrawn from said first power enable circuit and the current drawn fromsaid second power enable circuit; and in the event that the differenceexceeds an imbalance threshold, identify the one of the first and secondpower enable circuit whose current drawn is lower, and disable the MPSfunctionality associated with the lower current drawn.
 3. A power overEthernet (PoE) power monitoring arrangement for monitoring powerdelivered to a powered device over communication cabling, thearrangement comprising: a control circuitry; a first power sourcingequipment (PSE) responsive to said control circuitry, said first PSEcomprising: a first output port arranged for connecting to the powereddevice over a first set of wires; a first power enable circuit; and afirst maintain power signature (MPS) functionality arranged to comparethe current drawn from said first power enable circuit to a firstundercurrent threshold, and disable said first power enable circuit inthe event that said current drawn from said first power enable circuitover a predetermined window is less than the first undercurrentthreshold, a second PSE responsive to said control circuitry, saidsecond PSE comprising: a second output port arranged for connecting tothe powered device over a second set of wires; a second power enablecircuit; and a second MPS functionality arranged to compare the currentdrawn from said second power enable circuit to a second undercurrentthreshold, and disable said second power enable circuit in the eventthat said current drawn from said second power enable circuit over apredetermined window is less than the second undercurrent threshold,said control circuitry arranged to: receive an indication that thepowered device presents a single powered device interface to both saidfirst and said second PSE; and control one of said first and second MPSfunctionality responsive to said received indication, wherein saidcontrol of one of said first and second MPS functionality, comprises:monitor the difference between the voltage output from said first powerenable circuit and the voltage output from said second power enablecircuit; and in the event that the difference exceeds an imbalancethreshold, identify the one of the first and second power enable circuitwhose voltage is higher, and disable the MPS functionality associatedwith the higher voltage output.
 4. A power over Ethernet (PoE) powermonitoring arrangement for monitoring power delivered to a powereddevice over communication cabling, the arrangement comprising: a controlcircuitry; a first power sourcing equipment (PSE) responsive to saidcontrol circuitry, said first PSE comprising: a first output portarranged for connecting to the powered device over a first set of wires;a first power enable circuit; and a first maintain power signature (MPS)functionality arranged to compare the current drawn from said firstpower enable circuit to a first undercurrent threshold, and disable saidfirst power enable circuit in the event that said current drawn fromsaid first power enable circuit over a predetermined window is less thanthe first undercurrent threshold, a second PSE responsive to saidcontrol circuitry, said second PSE comprising: a second output portarranged for connecting to the powered device over a second set ofwires; a second power enable circuit; and a second MPS functionalityarranged to compare the current drawn from said second power enablecircuit to a second undercurrent threshold, and disable said secondpower enable circuit in the event that said current drawn from saidsecond power enable circuit over a predetermined window is less than thesecond undercurrent threshold, said control circuitry arranged to:receive an indication that the powered device presents a single powereddevice interface to both said first and said second PSE; and control oneof said first and second MPS functionality responsive to said receivedindication, wherein said control of one of said first and second MPSfunctionality, comprises: monitor the difference between the currentdrawn from said first power enable circuit and the current drawn fromsaid second power enable circuit; and adjust one of said firstundercurrent threshold and said second undercurrent threshold responsiveto said monitored difference.
 5. A power over Ethernet (PoE) powermonitoring arrangement for monitoring power delivered to a powereddevice over communication cabling, the arrangement comprising: a controlcircuitry; a first power sourcing equipment (PSE) responsive to saidcontrol circuitry, said first PSE comprising: a first output portarranged for connecting to the powered device over a first set of wires;a first power enable circuit; and a first maintain power signature (MPS)functionality arranged to compare the current drawn from said firstpower enable circuit to a first undercurrent threshold, and disable saidfirst power enable circuit in the event that said current drawn fromsaid first power enable circuit over a predetermined window is less thanthe first undercurrent threshold, a second PSE responsive to saidcontrol circuitry, said second PSE comprising: a second output portarranged for connecting to the powered device over a second set ofwires; a second power enable circuit; and a second MPS functionalityarranged to compare the current drawn from said second power enablecircuit to a second undercurrent threshold, and disable said secondpower enable circuit in the event that said current drawn from saidsecond power enable circuit over a predetermined window is less than thesecond undercurrent threshold, said control circuitry arranged to:receive an indication that the powered device presents a single powereddevice interface to both said first and said second PSE; and control oneof said first and second MPS functionality responsive to said receivedindication, wherein: said first PSE further comprises a first powerattribute detector arranged to detect a second power attributeassociated with said first output port; said second PSE furthercomprises a second power attribute detector arranged to detect a secondpower attribute associated with said second output port, and whereinsaid control circuitry is further arranged to: obtain from said firstpower attribute detector an indication of the second power attributeassociated with said first output port; obtain from said first powerattribute detector an indication of the second power attributeassociated with said first output port; of each of said pair of PSEs anindication of said detected second power attribute; and compare saidobtained indications, said control of one of said first and second MPSfunctionality responsive to said comparison.
 6. The arrangement of claim5, wherein the second power attribute associated with said first outputport comprises a representation of the value of a voltage across saidfirst output port; and the second power attribute associated with saidsecond output port comprises a representation of the value of a voltageacross said second output port.
 7. A method for monitoring powerdelivered to a powered device over communication cabling, the methodcomprising: enabling a first supply power, a function of a current ofsaid enabled first supply power arranged to flow through a first outputport to the powered device; enabling a second supply power, a functionof a current of said enabled second supply power arranged to flowthrough a second output port to the powered device; for said enabledfirst supply power, providing a first maintain power signature (MPS)functionality arranged to compare the current drawn from said enabledfirst supply power to a first undercurrent threshold, and disable saidenabled first supply power in the event that said current drawn fromsaid enabled first supply power over a predetermined window is less thanthe first undercurrent threshold; for said enabled second supply power,providing a second maintain power signature (MPS) functionality arrangedto compare the current drawn from said enabled second supply power to asecond undercurrent threshold, and disable said enabled second supplypower in the event that said current drawn from said enabled secondsupply power over a predetermined window is less than the secondundercurrent threshold; receiving an indication that the powered devicepresents a single powered device interface to both said first and saidsecond enabled supply power; and controlling one of said provided firstand second MPS functionality responsive to said received indication,wherein said controlling of one of said first and second MPSfunctionality, comprises: disabling both of said first and second MPSfunctionality; monitoring the sum of the current drawn from said firstsupply power and the current drawn from said second supply power; and inthe event that the sum of the currents drawn exceeds a combinationthreshold, disabling both said first supply power and said second supplypower.
 8. A method for monitoring power delivered to a powered deviceover communication cabling, the method comprising: enabling a firstsupply power, a function of a current of said enabled first supply powerarranged to flow through a first output port to the powered device;enabling a second supply power, a function of a current of said enabledsecond supply power arranged to flow through a second output port to thepowered device; for said enabled first supply power, providing a firstmaintain power signature (MPS) functionality arranged to compare thecurrent drawn from said enabled first supply power to a firstundercurrent threshold, and disable said enabled first supply power inthe event that said current drawn from said enabled first supply powerover a predetermined window is less than the first undercurrentthreshold; for said enabled second supply power, providing a secondmaintain power signature (MPS) functionality arranged to compare thecurrent drawn from said enabled second supply power to a secondundercurrent threshold, and disable said enabled second supply power inthe event that said current drawn from said enabled second supply powerover a predetermined window is less than the second undercurrentthreshold; receiving an indication that the powered device presents asingle powered device interface to both said first and said secondenabled supply power; and controlling one of said provided first andsecond MPS functionality responsive to said received indication, whereinsaid controlling of one of said first and second MPS functionality,comprises: monitoring the difference between the current drawn from saidfirst supply power and the current drawn from said second supply power;and in the event that the difference exceeds an imbalance threshold,identifying the one of the first and second supply power whose currentdrawn is lower, and disabling the MPS functionality associated with thelower current drawn.
 9. A method for monitoring power delivered to apowered device over communication cabling, the method comprising:enabling a first supply power, a function of a current of said enabledfirst supply power arranged to flow through a first output port to thepowered device; enabling a second supply power, a function of a currentof said enabled second supply power arranged to flow through a secondoutput port to the powered device; for said enabled first supply power,providing a first maintain power signature (MPS) functionality arrangedto compare the current drawn from said enabled first supply power to afirst undercurrent threshold, and disable said enabled first supplypower in the event that said current drawn from said enabled firstsupply power over a predetermined window is less than the firstundercurrent threshold; for said enabled second supply power, providinga second maintain power signature (MPS) functionality arranged tocompare the current drawn from said enabled second supply power to asecond undercurrent threshold, and disable said enabled second supplypower in the event that said current drawn from said enabled secondsupply power over a predetermined window is less than the secondundercurrent threshold; receiving an indication that the powered devicepresents a single powered device interface to both said first and saidsecond enabled supply power; and controlling one of said provided firstand second MPS functionality responsive to said received indication,wherein said controlling of one of said first and second MPSfunctionality, comprises: monitoring the difference between the voltageoutput from said first supply power and the voltage output from saidsecond supply power; and in the event that the difference exceeds animbalance threshold, identifying the one of the first and second supplypower whose voltage is higher, and disabling the MPS functionalityassociated with the higher voltage output.
 10. A method for monitoringpower delivered to a powered device over communication cabling, themethod comprising: enabling a first supply power, a function of acurrent of said enabled first supply power arranged to flow through afirst output port to the powered device; enabling a second supply power,a function of a current of said enabled second supply power arranged toflow through a second output port to the powered device; for saidenabled first supply power, providing a first maintain power signature(MPS) functionality arranged to compare the current drawn from saidenabled first supply power to a first undercurrent threshold, anddisable said enabled first supply power in the event that said currentdrawn from said enabled first supply power over a predetermined windowis less than the first undercurrent threshold; for said enabled secondsupply power, providing a second maintain power signature (MPS)functionality arranged to compare the current drawn from said enabledsecond supply power to a second undercurrent threshold, and disable saidenabled second supply power in the event that said current drawn fromsaid enabled second supply power over a predetermined window is lessthan the second undercurrent threshold; receiving an indication that thepowered device presents a single powered device interface to both saidfirst and said second enabled supply power; and controlling one of saidprovided first and second MPS functionality responsive to said receivedindication, wherein said controlling of one of said first and second MPSfunctionality, comprises: monitoring the difference between the currentdrawn from said first supply power and the current drawn from saidsecond supply power; and adjusting one of said first undercurrentthreshold and said second undercurrent threshold responsive to saidmonitored difference.
 11. A method for monitoring power delivered to apowered device over communication cabling, the method comprising:enabling a first supply power, a function of a current of said enabledfirst supply power arranged to flow through a first output port to thepowered device; enabling a second supply power, a function of a currentof said enabled second supply power arranged to flow through a secondoutput port to the powered device; for said enabled first supply power,providing a first maintain power signature (MPS) functionality arrangedto compare the current drawn from said enabled first supply power to afirst undercurrent threshold, and disable said enabled first supplypower in the event that said current drawn from said enabled firstsupply power over a predetermined window is less than the firstundercurrent threshold; for said enabled second supply power, providinga second maintain power signature (MPS) functionality arranged tocompare the current drawn from said enabled second supply power to asecond undercurrent threshold, and disable said enabled second supplypower in the event that said current drawn from said enabled secondsupply power over a predetermined window is less than the secondundercurrent threshold; receiving an indication that the powered devicepresents a single powered device interface to both said first and saidsecond enabled supply power; controlling one of said provided first andsecond MPS functionality responsive to said received indication;obtaining an indication of a second power attribute associated with saidfirst output port; obtaining an indication of a second power attributeassociated with said second output port; and comparing said obtainedindications, said controlling of one of said first and second MPSfunctionality responsive to said comparison.
 12. The method of claim 11,wherein the second power attribute associated with said first outputport comprises a representation of the value of a voltage across saidfirst output port; and the second power attribute associated with saidsecond output port comprises a representation of the value of a voltageacross said second output port.